Yanji is the capital of China’s Yanbian autonomous prefecture. It has a population of about 2.3 million, one-third of whom are ethnic Koreans. (Shin Woong-jae/For The Washington Post)

Every day of the week, Mrs. Kim gets up at 4:40 a.m. to prepare breakfast for the fifth-grade boy she looks after and get him ready for school. His parents, a Korean-Chinese couple, have gone to South Korea to work, so Mrs. Kim is the boy’s caretaker.

It’s barely light when she leaves the house to catch a bus to her next workplace, another home where she cooks breakfast and cleans the house. Then it’s another dash across town to prepare lunch and clean at her third job, before she heads to her fourth job to cook dinner for a family and give their house a once-over.

“I have so little time to clean these big houses. I have sweat dripping down my back,” says Mrs. Kim, a 62-year-old North Korean woman working in the northern Chinese border city of Yanji. She did not want to give her full name for fear of endangering her family at home in Chongjin, an industrial city on North Korea’s east coast.

At the end of her workday she arrives home after dark, exhausted, to tend to the boy. The next day, she will do it all again.

Although she is in China illegally, Mrs. Kim is not a defector from North Korea. She shows a pride in being North Korean and believes in the regime’s peculiar brand of hereditary communism. And she fully intends to return to Chongjin.

Tourists visit Tumen Border Bridge, which connects Tumen in China and Namyang in North Korea. (Shin Woong-jae/For The Washington Post)

She is instead part of a wave of North Koreans who are simply looking to earn money and sustain their families back home. Some work as cooks and nannies, like Mrs. Kim; others do odd jobs on farms or work in construction. Some young North Korean women are said to work in the sex trade.

Saturday, North Korea will celebrate the 70th anniversary of its Workers’ Party, the communist organization at the core of the state, with great fanfare. There will be a huge parade — complete with goose-stepping soldiers, dancing children and possibly a missile test — and the extolling of North Korea’s unyielding strength.

But beyond the spectacle, North Korea remains the world’s most hermetically sealed state, one run by an authoritarian regime that uses food and propaganda to keep the populace under control — and torture, political prison camps and executions to punish transgressors.

Yet unknown thousands of North Koreans are working outside the country and making money.

Many are sent abroad by the regime to earn foreign currency for the cash-strapped state, a practice that has been accelerated under Kim Jong Un, the 30-something, third-generation supreme leader who took control of the country after his father’s death in late 2011. But others toil abroad, independently and illegally, for their family’s survival.

In many ways, this is the new generation of divided Korean families. More than 60 years ago, families were divided when the Korean Peninsula was split. Now there are North Korean families who live apart as some go in search of food or freedom.

Mrs. Kim — neatly turned out in a blue lacy blouse and pressed gray pants, her short hair permed and her face carefully made up — was lucky to get out.

People buy street food near Yanbian University in Yanji, China. (Shin Woong-jae/For The Washington Post)

Since a devastating famine in the mid-1990s, the tide of North Koreans crossing the Tumen River into China has ebbed and flowed. First came waves of people who were starving, many of them young women who were sold to Chinese men.

As the situation in North Korea stabilized in the mid-2000s, Pyongyang realized that it could use access to this part of China as a kind of safety valve, allowing people to cross temporarily into China to earn what the state could no longer provide.

But harsh new restrictions have been imposed under Kim Jong Un. He has sharply increased security along the border, according to missionaries in the area who help the North Koreans who make it across, and North Korean soldiers have taken to hiding in dugouts, ready to ambush those trying to escape.

Over the past year, China has also heightened security with added police posts, since two incidents in which North Koreans, probably hungry, crossed the river and killed local Chinese.

Because Mrs. Kim has relatives in China, she was able to get an exit permit from North Korea, allowing her out for one month, and she entered China in December. It was her second time.

She didn’t want to come to China again, but she had to: Her husband is sick and needs medicine, and although her son and son-in-law have decent government jobs, they don’t earn enough to make ends meet.

Her daughter and daughter-in-law work in the market back home, the former selling secondhand clothes that Mrs. Kim sends them. But it’s expensive to smuggle clothes into North Korea, and there’s not much demand. “It’s like pouring water into a pot with a hole in it,” she said.

Mrs. Kim has found work with ethnic Korean families in China. She earns $550 a month, exponentially more than the $6 a month she earned as a schoolteacher in Chongjin. She sends $470 of her earnings home to her family, but by the time the money broker takes his commission — a hefty 30 percent — only $330 makes it through.

“Without this money, there wouldn’t be enough for them to eat,” she said, sitting on the floor in a borrowed apartment in downtown Yanji, a meeting place chosen so she wouldn’t be seen talking to foreign reporters.

Because she is here illegally, Mrs. Kim must watch her every move. Getting caught by the Chinese police would almost certainly mean repatriation to North Korea and a prison camp, or worse.

Her children would never take such a risk, she said. “They don’t think about crossing the border. They’re too scared to try.”

This life is clearly tough. Asked about her husband, Mrs. Kim started to cry — an unusual display of emotion among often-stoic North Koreans — and turned away to hide her face with her gnarled hands.

But she doesn’t ask for sympathy. She is simply doing what she must. “I can’t afford to think about my age or my health. I just have to think about making money for my family,” she said, adding that she hopes she’ll be able to bribe her way back into North Korea and avoid punishment for violating the terms of her month-long exit visa.

“I don’t know how long I’m going to stay, but I’m going to stay for a long time,” she said. And then her eyes started to well up again.

A reliance on brokers

As a result of the clampdown on both sides of the Tumen River, the number of people escaping from North Korea has dropped sharply.

Numbers are impossible to come by. But one missionary working in a town outside Yanji, who asked that neither he nor his location be named for fear of alerting local police to his activities, said that he has taken in only four North Koreans escaping the country so this year, compared with 10 in the same period last year.

A man who runs three shelters for North Koreans in Yanji has so little to do these days that he started driving as a part-time job.

Yanji is the dreary capital of the Yanbian autonomous prefecture. It has a population of about 2.3 million, one-third of whom are ethnic Koreans, although many of them have left in recent years for the higher wages — up to five times as high — in South Korea.

Parts of Yanji, with its mall and movie theater and cafes offering ostentatious desserts and free WiFi, look like South Korea. But other parts could easily be in North Korea.

Yoon lives in one of those: a small run-down village of ethnic Koreans just outside the city, in a dilapidated house with a wood-fired stove and an outside toilet.

Like Mrs. Kim, Yoon was lucky to get out.

A broker helped her escape from her small North Korean village just over the border two years ago, and she was married — or at least betrothed — to a ­Chinese-Korean man. Yoon, who is 33, says she did not pay the broker to help her escape, but local aid workers say it is highly likely that the man paid a fee for her.

Some people might still be able to make it out of North Korea the old-fashioned way: wading or swimming or skating across the river in the dead of night. But for the most part, escaping now requires money. Lots of it.

“It’s impossible to cross now without paying bribes or brokers,” said Kim Song-ryol, a church elder based in Yanji.

Bribing one’s way across from the border city of Musan, the site of a huge mine that is a major source of revenue for North Korea, now costs $800, missionaries here say. Crossing at Hyesan, 120 miles down the border, is much easier and requires only $300 to grease palms.

The price for arranging transit is much steeper. Brokers charge about $3,000 to get North Koreans from China to South Korea — and for a whopping $10,000 they can extract people from the North and get them to the South, local missionaries say. The North Korean intermediaries are usually soldiers.

Although she’s out, Yoon, who also asked that her full name be withheld to protect her family in North Korea, is trapped by the recent security clampdown.

Her intention was to work for a while to raise the money to bring out her 13-year-old daughter, and then both would go to South Korea. All was going according to plan until her North Korean broker was arrested.

“There is no way of getting my daughter out now,” Yoon said in an interview. It was the first time she had met a Westerner, and she was visibly nervous.

Yoon was struggling with what to do. Should she go to South Korea, where she could earn much more money and live legally, and send for her daughter from there?

Or should she keep working here — she earns about $400 a month putting in long hours as a cook in a restaurant owned by ethnic Koreans — and wait for the security situation to ease? She sometimes takes the bus to the river and stares across at North Korea, where her daughter lives with her mother.

“Maybe I could wait for her to grow up and then get her out?” she asked, thinking out loud.

In appearance, Yoon could easily pass for a local. She was wearing a pink flowery top and black sparkled leggings and had her long black hair pulled into a ponytail. Her eyebrows are tattooed on, a trend in this part of the world.

And although she takes the bus, she can’t talk to anyone or she will immediately reveal herself to be North Korean. She doesn’t speak Chinese, and her Korean has a very strong northern provincial accent.

Like Mrs. Kim, she’s in China illegally. But she’s not a migrant worker. She defected from North Korea and is desperate to reach the South, where the government will give her citizenship and where she will be able to live without fear and be able to communicate.

“Of course I’m nervous about living in China,” she said. “I’m afraid I’m going to be arrested if someone snitches on me or if I have an argument with someone.”

Pyongyang takes a particularly hard line against people who are considered to have “defected,” calling them “human scum.”

“I think about going to South Korea all the time,” Yoon said, beginning to relax a little. “If I was a lot older, I might give that up, but I’m still young, so I still have time to live in South Korea.”

More private enterprise

The number of people crossing this border has dropped markedly, but increased security is only part of the story. For some North Koreans, life has become a little better in recent years.

North Korea’s economy has become increasingly privatized as the state system has crumbled, and the regime is now tolerant, if not encouraging, of private enterprise. As a result, more money is in circulation and some people are doing better.

But older North Koreans, who have known only a communist way of life in which the state is supposed to provide everything, are struggling to adapt.

Indeed, even though she lives among the neon lights and bustle of China, Mrs. Kim has a lifetime of propaganda ingrained in her.

“Now that I’m living in China, I can see more clearly that it is the United States that is making our life more difficult,” she said, parroting the state’s excuse for North Korea’s backwardness. “It makes me understand how much North Korea could develop if it wasn’t being obstructed by America.”

She appears to genuinely believe this. But she knows she can no longer rely on the state to take care of her, and the questions have got her thinking. As she prepared to leave the borrowed apartment, she turned and asked, almost rhetorically: “Is life in South Korea really that much better?”

Then she disappeared into the dark corridor, off to her next job.

Yoonjung Seo contributed to this report.